Intra-individual daily and yearly variability in actigraphically recorded sleep measures: The CARDIA study

Department of Health Studies, University of Chicago, 5841 S. Maryland Ave, MC 2007, Chicago, IL, USA.
Sleep (Impact Factor: 4.59). 07/2007; 30(6):793-6.
Source: PubMed


To describe the day-to-day and year-to-year variation in sleep characteristics among early middle-aged adults.
Participants wore an Actiwatch (Mini Mitter, Inc) for 3 days on two occasions approximately 1 year apart.
N = 669 participants aged 38-50 years from the Chicago site of the Coronary Artery Risk Development in Young Adults (CARDIA) cohort study.
Sleep measures included sleep duration, sleep latency, sleep efficiency, and time in bed. For each sleep parameter, total variance was decomposed into between-subject variance, within-subject variance from day to day, and within-subject variance from year to year. The standard deviation was calculated from the variance. Analysis yielded a within-subject daily standard deviation (SD) of 1.26 hours and a within-subject yearly SD of 0.39 hours for sleep duration. Daily SD was 30.7 minutes and yearly SD was 6.3 minutes for within-subject variability of sleep latency. Daily SD was 8.4% and yearly SD was 2.7% for within-subject variability of sleep efficiency. Finally, daily SD was 1.31 hours and yearly SD was 0.52 hours for within-subject variability of time in bed.
For each of the 4 sleep characteristics, nightly variability was much greater than yearly variability, meaning sleep behavior changes little in one year in this cohort of early middle-aged adults, despite large daily fluctuations. These results have important methodological implications, including that single-day measures of sleep may not accurately reflect habitual behavior.

Download full-text


Available from: Kristen L Knutson
  • Source
    • "Dillon Q3 and colleagues (2014) identified that IIV in sleep was actually lower at older ages. Furthermore, compared with the literature support for IIV in sleep [13] [18] [27], less is known about IIV of pre-sleep arousal, and how pre-sleep arousal IIV may vary across ages. If pre-sleep arousal and sleep show considerable IIV, the traditional analytic approach of relying on the examination of mean values, or single measurements, may not be the most appropriate level of measurement for these variables [10]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Intraindividual variability is an often understudied aspect of health outcomes research that may provide additional, complementary information to average values. The current paper aims to further our understanding of intraindividual variability in health research by presenting the results of a daily diary study of sleep and pre-sleep arousal. Pre-sleep arousal is often implicated in poor sleep outcomes, although the arousal–sleep association is not uniform across age groups. The examination of intraindividual variability in different age groups may provide a more complete understanding of these constructs, which, in turn, can inform future research. The overall objectives of the current study are to quantify the amount of intraindividual variability in pre-sleep arousal and sleep and to examine age differences in this variability. A sample of older (n=50) and younger (n=50) adults recruited from North Central Florida and online completed 14-consecutive-day diaries assessing pre-sleep arousal and sleep outcomes. Significant age differences were found for sleep and pre-sleep arousal; older adults displayed poorer, more variable sleep for the majority of sleep outcomes, and higher levels of pre-sleep arousal than younger adults. The high amount of intraindividual variability has implications for the assessment of pre-sleep arousal and sleep across age groups.
    Full-text · Article · Mar 2015 · Sleep Science
  • Source
    • "Sleep fragmentation scores, or a measure of the restlessness of sleep, were estimated by summing the percentage of movement time with the percentage of time spent immobile for ≤1 min. A previous report found high continuity in the values recorded between the two waves for sleep duration [15]. Further information on the methods used in the CARDIA Sleep Study have been described [9]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Objective To determine the association between objectively measured sleep and 10-year changes in estimated glomerular filtration rate (eGFR). Methods From 2003 to 2005, an ancillary sleep study was conducted at the Chicago site of the Coronary Artery Disease in Young Adults (CARDIA) study. Community-based black and white adults (aged 32–51 years) wore a wrist actigraph up to six nights to record sleep duration and fragmentation. Sleep quality was measured with the Pittsburgh Sleep Quality Index (PSQI). Participants without history of cardiovascular or chronic kidney diseases, proteinuria, or hypertension at the 2000–2001 CARDIA examination were followed over 10 years (n = 463). eGFR was estimated from serum creatinine (eGFRCr) at the 2000–2001, 2005–2006, and 2010–2011 CARDIA examinations, whereas cystatin-C-estimated eGFR (eGFRCys) was measured at the 2000–2001 and 2005–2006 examinations. Generalized estimating equation regression and linear models estimated the associations of each sleep parameter with changes in eGFRCr and eGFRCys, controlling for cardiovascular and renal risk. Results Sleep parameters were not related to 5-year change in eGFRCys. However, each 1 h decrease in sleep duration was significantly associated with a 1.5 mL/min/1.73 m2 higher eGFRCr [95% confidence interval (CI), 0.2−2.7], and each one-point increase in PSQI was significantly associated with a 0.5 mL/min/1.73 m2 higher eGFRCr (95% CI, 0.04−0.9) over 10 years. Conclusion In this community-based sample, shorter sleep and poorer sleep quality were related to higher kidney filtration rates over 10 years.
    Full-text · Article · Sep 2014 · Sleep Medicine
  • Source
    • "Research with adult samples suggests systematic within-person variability in the three dimensions ( Akerstedt et al., 2012; Knutson, Rathouz, Yan, Liu, & Lauderdale, 2007; McCrae et al., 2008). For example, Gamaldo et al. (2010) showed substantial within-person variability of self-reported sleep duration and sleep quality in adults over eight measurement points (within 3 weeks). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Background Recent studies have suggested substantial fluctuations of cognitive performance in adults both across and within days, but very little is known about such fluctuations in children. Children's sleep behavior might have an important influence on their daily cognitive resources, but so far this has not been investigated in terms of naturally occurring within-person variations in children's everyday lives. Methods In an ambulatory assessment study, 110 elementary school children (8–11 years old) completed sleep items and working memory tasks on smartphones several times per day in school and at home for 4 weeks. Parents provided general information about the children and their sleep habits. Results We identified substantial fluctuations in the children's daily cognitive performance, self-reported nightly sleep quality, time in bed, and daytime tiredness. All three facets were predictive of performance fluctuations in children's school and daily life. Sleep quality and time in bed were predictive of performance in the morning, and afternoon performance was related to current tiredness. The children with a lower average performance level showed a higher within-person coupling between morning performance and sleep quality. Conclusions Our findings contribute important insights regarding a potential source of performance fluctuations in children. The effect of varying cognitive resources should be investigated further because it might impact children's daily social, emotional, and learning-related functioning. Theories about children's cognitive and educational development should consider fluctuations on micro-longitudinal scales (e.g., day-to-day) to identify possible mechanisms behind long-term changes.
    Full-text · Article · Jul 2014 · Journal of Child Psychology and Psychiatry
Show more